The function of A-B doors, also known as double interlocked doors, is that: the door B cannot be opened when the door A is open, and can be opened only when the door A is closed; conversely, the door A cannot be opened when the door B is open. In other words, the two doors each locks the other. A-B doors are usually used in the entrances and exits of important premises such as banks, prisons, and vaults. FIG. 1 is a schematic view of an application scenario of A-B doors, which includes a public area, a door A, a transit area, a door B, and a supervised area. A host of the system with A-B doors is connected to, respectively, an entrance access control and an exit switch button at the door A, an entrance access control and an exit switch button at the door B, and an electronic authorization conversion device between the A-B doors.
When a cardholder swipes a card at the entrance access control of the door A, the entrance access control reads the card number and sends it to the host. When the host determines that the card number has the authorization to pass through the door A, it sends an opening command to the entrance access control. After the person has entered the transit area, an electronic authorization conversion is performed, that is, the host controls the electronic authorization conversion device, so that the electronic authorization conversion device converts the authorization of the card to the door B, after which the cardholder can open the door B.
When the person returns from the supervised area to the public area, the door A and the door B can be opened by means of the two exit switch buttons.
In the prior art, after a person has passed the verification at the door A from the public area and undergone the electronic authorization conversion, the authorization of the person's card is converted to the door B. In other words, the person can pass the verification at the door B and enter the supervised area.
However, if the card of the person is lost or stolen in the supervised area, then the card may still have the authorization for the door B, which will pose a certain risk to the security of the A-B doors. For example, if an unauthorized person obtains a card authorized for the door B, then the unauthorized person can enter the transit area by hacking the authorization for the door A, and then pass the verification at the door B by using the obtained card and enter the supervised area.